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Frankenbrakes and brake improvement discussion

Udi

Udi

RM Chief Ornithologist
Mar 14, 2005
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Sandwich said:
I guess more pistons makes sense to me, as all of that power is translated through the pad to the rotor
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Yeah, basic theory says pad size makes no difference since F=PA and a bigger pad just means less force per unit area, but technically there are two points that do give more pistons some advantage: a) bigger pad area = better heat dissipation which I'm sure you knew (though maguras don't really benefit with their "4 pad" split nonsense, one big pad like M810/820 and E4/V4 does) , and b) the center of force application is further out on a 4-pot brake compared to a big 2-pot, so even for identical total slave area which would give identical hydraulic leverage, the 4-pot would actually have a small mechanical leverage advantage at the rotor.

So you can still be correct for those two reasons. :D
 
T

tabletop84

Monkey
Nov 12, 2011
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Sandwich said:
My mt5s have been just OK. Power on tap, but you have to work for it. Not like some other brakes that have power in spades without needing a solid squeeze. Certainly weaker than my 810s and possibly my 785s, but stronger than a hayes mag or formula T1s.

So, more power = better.
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Weird. Everyone seems to think MT5 is a far better brake than the Shimanos. But when I semi-retired in 2015 Shimano was the Benchmark so I'm wondering if I should give the MT5 a go or not. As I'm really scrawny and even slower than two years ago I doubt I'll need more power than the 785. But I certainly want the foolproof bleeding-ability...
 
iRider

iRider

Turbo Monkey
Apr 5, 2008
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Jm_ said:
You shut your dirty whore mouth!


One important thing to note is that this is the rear brake, so we can expect at least 8 pistons on the front.
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Nah, thanks to the soon to be release Boost 130 front wheel standard you have space for two discs in the front, one on the left and one on the right. The BBF(TM) (BalancedBrakeForce) will stop the twisting of suspension forks under braking loads and enable 3.75% better suspension action. Look at Moto GP bikes, proven concept.
That way 2 x 6 pot calibers will be enough.
 
Sandwich

Sandwich

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May 23, 2002
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tabletop84 said:
Weird. Everyone seems to think MT5 is a far better brake than the Shimanos. But when I semi-retired in 2015 Shimano was the Benchmark so I'm wondering if I should give the MT5 a go or not. As I'm really scrawny and even slower than two years ago I doubt I'll need more power than the 785. But I certainly want the foolproof bleeding-ability...
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I can't comment about anyone besides myself. I have OEM MT5s from ribble, I believe they have performance pads, and they are powerful enough and fade resistant enough, but they have not impressed me the way that my saint 810s had. Those brakes had power to spare and virtually never faded. My 785s, if I recall correctly, were a bit more similar to the mt5s in power. Not in modulation, the mt5s are worlds better modulators than any shimano brake...but whether you need that ability to feather in DH as much as you do while trail riding...I guess that's up to you.

I have the new pads on order and will hopefully get out DHing in a few weeks. I'll try and do a run on the performance pads before I swap in the race pads to confirm any changes.

I'm not the be-all end all judge on brakes, so my experience is an n of 1. I've had some powerful brakes before (810s, gustavs) and some terrible ones (hope dh04), and plenty of mediocre ones (Hayes Mag, anything else by hayes, maybe the formula T1S), but I don't ride as much as most people nowadays. I just expected these things to throw me through a wall and they're just OK. Minimal fade and phenomenal modulation, but just OK power.
 
norbar

norbar

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Jun 7, 2007
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Sandwich said:
interesting, i had read somewhere that they had basically no power, which also made sense.
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They have no power for like 95% of the lever throw but then the bite point was super instant. I really like brakes with no modulation, I was raised on magura gustav m but those are retarded. Though it's hard to judge power when it's so instantaneous. Even u-brakes can lock your wheel.
 
Sandwich

Sandwich

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I hated my gustavs for that reason. First day I took them out was rainy/mud slicked, and it was a disaster. Just locking up everywhere.
 
norbar

norbar

KESSLER PROBLEM. Just cause
Jun 7, 2007
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Sandwich said:
I hated my gustavs for that reason. First day I took them out was rainy/mud slicked, and it was a disaster. Just locking up everywhere.
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2nd gen was better at that. Also the long lever helped with that problem. I really liked 2nd gen Gustavs
 
Jm_

Jm_

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Jan 14, 2002
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norbar said:
2nd gen was better at that. Also the long lever helped with that problem. I really liked 2nd gen Gustavs
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With SlowLeak™ technology, even the 1st gens were manageable with good modulation.
 
kidwoo

kidwoo

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Just got some XT levers on some Cura calipers. Spin around the block indicates possible success.

xt levers
cura hoes
shimano olive and dildo
Formula mineral oil


We'll see how that goes. The cura setup doesn't retract the pads very much from the rotor. Kinda hoping this helps that a little.
 
Udi

Udi

RM Chief Ornithologist
Mar 14, 2005
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That's awesome!

Who's guinea pigging?

I'm pleased about this as I had an idea in mind for my next frankenbrake but it involved the XT caliper not being an unreliable leaky POS. I was going to fit the 22mm alloy pistons from the old M800 calipers I have, but a brand new option with fresh seals included sounds like a goer.
 
Gary

Gary

"S" is for "neo-luddite"
Aug 27, 2002
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Skip to 5:54


Jesus has answered all your prayers! You do all pray, right?
 
kidwoo

kidwoo

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Jm_ said:
Now there is this, a solution to all of your leaky non-serviceable shimano pistons?

http://www.ebay.com/itm/282489847007

Course...they are metal...
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They can't even take the time to change the word 'car' to 'bike' in the description.


Nothing sketchy, that doesn't work, or breaks on the first use has ever come out of someone in china selling things on ebay so I'm sure those are sick.

These ones have lightning bolts and say 'power'.

http://www.ebay.com/itm/For-shimano-M675-M785-M7000-M8000-Brand-New-Ceramic-Type-Piston-Fixes-One-Pair/192169954193?_trksid=p2047675.c100009.m1982&_trkparms=aid=888007&algo=DISC.MBE&ao=1&asc=41451&meid=7fc83a8adbca435c80a215f1ef194148&pid=100009&rk=1&rkt=1&sd=282489847007

they're cheap at least
 
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Udi

Udi

RM Chief Ornithologist
Mar 14, 2005
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kidwoo said:
Nothing sketchy, that doesn't work, or breaks on the first use has ever come out of someone in china selling things on ebay so I'm sure those are sick.
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Shimano brakes from factory are currently sketchy, sometimes fail completely without user error, and occasionally even leak *before* first use.

I've seen stuff come out of HK/TW/China that is designed and manufactured better than the "real" deal increasingly often. Good on them for having a go at fixing a problem that Shimano has refused to address for years.

kidwoo said:
The cura setup doesn't retract the pads very much from the rotor. Kinda hoping this helps that a little.
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It physically can't do that because slave piston rollback is a function of caliper seal geometry (nothing to do with the lever). I think your combo should net a more powerful brake though, and anyway it's probably better the rollback isn't magically increased so that the throw stays reasonable.
 
kidwoo

kidwoo

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Udi said:
Shimano brakes from factory are currently sketchy, sometimes fail completely without user error, and occasionally even leak *before* first use.

I've seen stuff come out of HK/TW/China that is designed and manufactured better than the "real" deal increasingly often. Good on them for having a go at fixing a problem that Shimano has refused to address for years.


It physically can't do that because slave piston rollback is a function of caliper seal geometry (nothing to do with the lever). I think your combo should net a more powerful brake though, and anyway it's probably better the rollback isn't magically increased so that the throw stays reasonable.
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Exactly. It's sketchy things from china I'm trying to fix :D

But it's still the wild west. I mentioned the price for a reason. It's not exactly a huge commitment.
 
Jm_

Jm_

sled dog's bollocks
Jan 14, 2002
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kidwoo said:
They can't even take the time to change the word 'car' to 'bike' in the description.


Nothing sketchy, that doesn't work, or breaks on the first use has ever come out of someone in china selling things on ebay so I'm sure those are sick.

These ones have lightning bolts and say 'power'.

http://www.ebay.com/itm/For-shimano-M675-M785-M7000-M8000-Brand-New-Ceramic-Type-Piston-Fixes-One-Pair/192169954193?_trksid=p2047675.c100009.m1982&_trkparms=aid=888007&algo=DISC.MBE&ao=1&asc=41451&meid=7fc83a8adbca435c80a215f1ef194148&pid=100009&rk=1&rkt=1&sd=282489847007

they're cheap at least
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Yeah, evidently you have never used Elixrs.
 
Mo(n)arch

Mo(n)arch

Turbo Monkey
Dec 27, 2010
4,441
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Actually it seems like 220mm rotors are getting more popular in WC races. Hill seemed to use them in Ft. Bill as well as Branigan:




They both ran adapters at the fork. Sram discs available in 220mm soon?
 
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